1. Field of the Invention:
The present invention relates to a novel process for the preparation of thermally stable copolymers comprising recurring imide/amide and diorganopolysiloxane structural units.
2. Description of the Prior Art:
The combination of recurring imide/amide and diorganopolysiloxane structural units has to date been advantageously used in the preparation of polymers which can be employed in insulating coating applications, for which the coating must have an excellent thermal stability. Representative prior art which describes polymers of this type includes U.S. Pat. Nos. 3,723,385 and 4,395,527. In these patents, polyimidoamides are described which contain diorganopolysiloxane recurring units which are the product of a condensation reaction in solution between a diprimary diamine containing a diorganopolysiloxane group, whether alone or in admixture with another diprimary organic diamine, and a monoanhydride of a tricarboxylic acid. However, such a process presents the disadvantage, common to the majority of processes where an amine reactant is reacted with an organic compound containing a carboxylic acid anhydride functional group, of requiring a cyclizing dehydration of the polyamic acid intermediates. Indeed, since this reaction forms an equilibrium, the water released must be removed, and this operation cannot generally be carried out completely in solution.